Liquid quality evaluating apparatus

ABSTRACT

This is an electrical apparatus for rapidly determining the quality of a liquid such as automotive brake fluid by comparing its boiling point with a predetermined reference value. Liquid to be tested is heated to its boiling point in a first vessel having a nozzle opening into a second vessel so as to transfer liquid when boiled from the first to the second vessel. Temperature rise to a predetermined value in the first vessel produces one signal and the presence of boiled liquid in the second vessel produces a second signal. Comparison of the time of occurrence of the two signals indicates the relation of the boiling point of the sample to the predetermined reference value.

United States Patent. 1191 Mizutani et al.

[451 Oct. 29, 1974 LIQUID QUALITY EVALUATING 3,107,5l6 10/1963 Markey73/17 APPARATUS [75] Inventors: Masumi Mizutan i, Gifu; Fukuo PrimaryExami"e' llerbert Goldstein Ham Tokyo. Hiram Kamamni Attorney, Agent, orFzrm-Kemon, Palmer & Yokohama, all of Japan Estabmok [731 Assignees:Showa Industries Co. Ltd.

Gigu-ken; Kitoku Cot, Ltd Tokyo; [57] ABSTRACT Fujisoku Electric Co.,Ltd., This is an electrical apparatus for rapidly determiningKawasaki-shi, all of, Japan the quality of a liquid such as automotivebrake fluid by comparing its boiling point with a predetermined [22]1973 reference value. Liquid to be tested is heated to its [21] App].No.: 328,373 boiling point in a first vessel having a nozzle openinginto a second vessel so as to transfer liquid when boiled from the firstto the second vessel. Tempera- [52] US. Cl. 73/17 A, 340/236 tum rise toa predetermined value in the first vessel [51] Int. Cl. G0lh 25/10, G08b23/00 [58]. Field of Sear h 73/17 61 1 324/65 R produces one signal andthe presence of boiled l1qu1d c h 340/236 6 in the second vesselproduces a second signal. Comparison of the time of occurrence of thetwo signals indicates the relation of the boiling point of the sam- [56]References cued pie to the predetermined reference value.

UNITED STATES PATENTS 0 3,034,535 4/1963 Markey 73/17 6 Chums 10 Drawmgl4 l5 if k l 23 25 i-: CONDUCTION 2 SEiEE'ilw 4:.

B; CIRCUIT S 16 LIQUID TEMPER- ATURE DETECTION CIRCUIT PATENTED um 29I974 I V 2&-

CONDUCTION CURRENT DETECTION CIRCUIT LIQUID TEMPER- ATURE DETECTIONCIRCUIT DC. AMPLIFIER PATENTEDUBTZQ I914 59 am am a FIG. 6

COUNTER FIG. 9A'

FIG 9B a l LIQUID QUALITY EVALUATING APPARATUS BACKGROUND OF THEINVENTION This invention relates to a liquid quality evaluatingapparatus for evaluating the quality of any liquid such as a brake fluidfor automobiles.

Recent tendency has been towards using a brake fluid as high in boilingpoint as possible so as to enhance brake performance. In general,however, the higher the initial boiling point, the greater the drop ofthe boiling point due to its hygroscopic property and the degenerationof the brake fluid due to its hygroscopicity now presents a problem. Asis known the brake fluid decreases in boiling point with-an increase inthe percentage of contained water. On the other hand brake fluid reachesa high temperature at the time of brake operation, particularly when agreater amount of braking force such as on a steep downhill road isrequired. If the brake fluid reaches its boiling point during the timeof brake operation, what is called a vapor lock phenomenon" occurs withthe result that the braking force is lowered to an extreme extent,presentinga possible greater peril under which an unexpected trafficaccident can take place. It is necessary, therefore, to exchange thedegenerated brake fluid reaching a certain water content for a new one.The necessity for exchange has heretofore been determined by judging thefrequency of uses without resort to checking the quality of a used brakefluid, or by sampling the brake fluid and chemically analyzing itsconstituents. In the former case however, a still usable brake fluid maybe discarded with the attendant uneconomical result, since no checkingis made as to the, usability of the brake fluid. Furthermore, even arelatively fresh brake fluid or one left unused, when placed in moist orhumid environments such as in a rainy season, reaches more than acertain water content (usually 3 percent) than expected, and its use isstill continued without the knowledge that its has become dangerous. Inthe latter case, a relatively intricate chemical analysis, as well as arelatively long period of time, is required with the attendantdisadvantages.

A liquid, in general, to say nothing of a brake fluid for automobiles,when an impurity is included therein, shows the property that itsboiling point varies.

Accordingly the object of this invention is to provide a liquid qualityevaluating apparatus capable of determining in a relatively simple wayand in a short period of time whether any sample liquid is good or bad,by electrically detecting whether or not its boiling point exceeds apredetermined temperature level.

SUMMARY OF THE INVENTION A liquid quality evaluating apparatus accordingto a preferred embodiment of this invention comprises: a sealed vesselmade of a heat conductive material contained therein a predeterminedamount of sample liquid and provided with a nozzle projecting in anintegral fashion from a predetermined side wall thereof so that asection of the nozzle is at least higher in level than the upper surfaceof the sample liquid contained within the sealed vessel; a heatingsource including a heater disposed in proximity with the sealed vesseland a power source connected across the heater; another vessel made ofan electric conductive material into which the sample liquid boiledthrough the heating of the heating source is forced through the nozzle;a needle-like electrode whose one end is arranged within thesecondmentioned vessel in a manner to be in contact with the boiledsample liquid; a conduction current detecting circuit having-an activecircuit element whose input electrode is connected to a bias powersource including the second-mentioned vessel, the boiled sample liquidpoured into this vessel, the needle-like electrode and a first D.C.power source and whose output electrode is connected via an excitationcoil with a core to the first D.C. source; a rotatable metal piece of amagnetic conductive material provided in proximity to the core of theconduction current detecting circuit and adapted to beelectromagnetically attracted with its one end as a fulcrum when theconduction current detecting circuit is actuated; a temperatureindicating meter continuously indicating the temperature variation ofthe sample liquid within the first mentioned vessel and constituting abridge circuit constructed of three resistors and a heat responsiveresistance element partly received in the first-mentioned vessel in amanner to be dipped in the sample liquid, a second D.C. power sourceconnected acorss the paired input terminals of the bridge circuit and atemperature indicating meter consisting of a conventional D.C.galvanometer connected across the paired output terminals of the bridge,circuit; and means for locking the deflection of the pointer of thetemperature indicating meter by the metal piece at the moment the metalpiece is attracted to the core of the conduction current detectingcircuit.

According to the liquid quality evaluating apparatus so constructed thetemperature indicating meter can continuously detect the temperaturevariation of the sample liquid within the first-mentioned vessel whichis heated by the heating source, and is adapted to lock the deflectionof the temperature indicating meter pointer in a position representativeof a boiling point of the sample liquid at the moment it is boiled.Therefore, if the boiling temperature range of a fresh reference liquidthe same as the sample liquid is preliminarily known, a temperatureindicated by the locked pointer on the temperature indicating metermakes the ready evaluation of the quality of the sample liquid accordingto whether said indicated temperature falls within the preset boilingtemperature range of the reference liquid.

A liquid quality evaluation apparatus according to another embodiment ofthis invention uses, in place of the metal piece of the first embodimentof this invention, a first normally closed contact and first normallyopen circuit both driven by the excitation coil included in theconduction current detecting circuit. There is also used, in place of atemperature indicating meter as shown in the first embodiment of thisinvention, a liquid temperature detecting circuit consisting of meansfor detecting the variation of the resistance of the heat sensitiveresistance element as the variation of an amount of electric current, aD.C. amplifier for amplifying the variation of the amount of electriccurrent so detected by said means, a Schmidt circuit connected to theD.C. amplifier, and an excitation circuit coupled to the Schmidt circuitand having an excitation .coil connected between the output terminalthereof and a D.C. source so as to drive a second normally open contactand second normally closed contact. A first series circuit consisting ofthe first normally closed contact, the second normally opened circuitand a first lamp and a second series circuit consisting of the firstnormally open contact, the secondnormally closed contact and a Secondlamp are connected in parallel between both the terminals of the DC.power source. With the liquid quality evaluating apparatus soconstructed, when the conduction current detecting circuit is renderedconductive earlier than the liquid temperature detecting circuit, thesecond lamp is lighted earlier than the first lamp. On the contrary,when the liquid temperature detecting circuit is rendered conductiveearlier than the conduction current detecting circuit, the first-lamp islighted earlier than the second lamp. Aliquid, in general, exhibits theproperty that when any inpurity is contained therein its boiling pointis raised or dropped with an increase of the impurity content.

Therefore, if a threshold voltage level of the Schmidt circuit in theliquid temperature detecting circuit is preset at the levelrepresentative of a temperature corresponding to a temperatureimmediately below a lower boiling point limit of a fresh referenceliquid the same as the sample liquid i.e. a reference liquid whoseimpurity content is below a predetermined value, or at the levelrepresentative of atemperature corresponding to a temperatureimmediately above a upper boiling point limit thereof, then'whether thesample liquid is good or bad can be determined by knowing which of thefirst and second lamps is lighted first.

The above-mentioned first and second series circuits can be replaced bya series circuit of a lamp and a normally open contact closed by theexcitation coil of the conduction current detecting circuit and a seriescircuit of a lamp and a normally open contact closed by the excitationcoil of the liquid temperature detecting circuit.

A liquid quality evaluating apparatus according to further embodiment ofthis invention comprises a ves sel made of a heat conductive andelectroconductive material into which a suitable amount of sample liquidis poured; aheating source having a heater arranged in proximity to thevessel and a power source connected across the ends of the heater; aneedle-like electrode whose one end is arranged within the vessel in amanner to be in contact with the sample liquid; a current conductionpath consisting of the needle-like electrode, the sample liquid, thevessel, a DC. power source and a resistor; a Schmidt circuit receptiveto a voltage drop appearing across the resistor in the currentconduction path when the sample liquid is heated, through the vessel bythe heating source, to a preset temperature corresponding to atemperature immediately below the lower boiling point limit of a freshreference liquid the same as the sample liquid, or to a temperatureimmediately above the upper boiling point limit thereof; and a countercoupled to the Schmidt circuit.

With the liquid quality evaluating apparatus so constructed, if noboiling occurs when the sample liquid is heated to the aforesaidpredetermined temperature, the input voltage level of the Schmidtcircuit is substantially constant and the count number of the counter isl or 0. On the other hand, if boiling takes place, the sample liquidforms bubbles corresponding to the impurity content therein, andcorresponding pulsating signals are applied to the Schmidt circuit.Therefore, if the threshold voltage of the Schmidt circuit is so presetthat binary coded signals corresponding to the number of the pulsatingsignals from the Schmidt circuit are driven, the number of thebinarycoded signals are counted bythe counter, and whether the sample liquidis good or bad can be evaluated according to the number of countsinvolved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagramshowing one embodiment of a liquid quality evaluating apparatusaccording to this invention;

FIG. 2 is a practical circuit diagram of the conduction currentdetecting circuit of FIG. 1;

FIG. 3 is a practical circuit diagram of the liquid temperaturedetecting circuit of FIG. 1;

FIG. 4 is a schematic block diagram showing one modification of theembodiment of FIG. 1;

FIG. 5 is a schematic block diagram showing another embodiment of aliquid quality evaluating apparatus according to this invention;

FIG. 6 is an enlarged front view showing the dial plate portion of atemperature indicating meter of FIG.

FIG. 7 is an enlarged sectional view illustrating a preferred example ofthe cover for the heating vessel shown in FIGS. 1, 4 and 5;

FIG. 8 shows a schematic block diagram showing further embodiment of aliquid quality evaluating apparatus according to this invention; and

FIGS. 9A and 98 respectively show input and output waveforms of theSchmidt circuit in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic blockdiagram of one embodiment of this invention. In the figure, referencenumeral 11 denotes a heating vessel made of a heat conducting materialsuch as copper, the vessel {ll having a sufficient capacity to-holdabout 0.6cc of liquid and an upper opening measuring about 10mm indiameter and presenting a substantially U-shaped longitudinal crosssection placed in the heating vessel 11 is about 0.5cc

V of an automobile brake fluid 12 to be evaluated. Then,

a sealing cover 13 is placed on the top of the vessel 11. From a sidewall of the heating vessel 11, for example, from the lower side wallthereof as shown in the figure, a nozzle 15 having an inner diameter ofabout 2mm projects in an integral fashion. A section'of the nozzle is ata higher level than the upper surface 14 of the brake fluid 12 in thevessel. At the bottom of the heating vessel a heater 18 is disposed inseries with a temperature adjusting variable resistor 17. The brakefluid 12 within the heating vessel 11 can thus be heated to about -300Cby an appropriate power source 16 When the brake fluid 12 within theheating vessel 11 boils, it is rapidly forced through the open end ofthe nozzle 15 (due to vapor pressure of the boiled brake within thesealed vessel 11) into another vessel 19 made of a electroconductivematerial such as brass having substantially the same capacity andconfiguration as the heating vessel 11. Within the vessel 19 there isdisposed a needle-like electrode 20 one end of which is permitted tocontact the boiled brake fluid. The other end of the electrode 20 isconnected to a positive terminal 22 ofa DC. power source 21 of about 12volts and integrally secured through an insulating material 23 such asporcelain to the vessel 19, the negative terminal of the DC. source 21being connected to ground. The positive terminal 22 of the DC. source 21is connected to the vessel I9 through a conduction current detectioncircuit 25 (as will be later described with reference to FIG. 2) to theoutput terminal of which is connected an excitation coil 24. Theconduction current detecting circuit 25 is normally open circuited, butwhen the brake fluid 12 within the heating vessel 11 is boiled andforced into the vessel '19, a current conduction path is establishedwith respect to the DC. power source 22 through the electrode 20, theboiled brake fluid 12, the vessel19 and the conduction current detectingcircuit 25, thereby causing excitation of the coil 23. To electricallydetect the temperature variation of the brake fluid 12 within theheating vessel 11, there is received in a fluid-tight fashion in theheating vessel 11 a heat responsive resistance element 26. This could bea metal-coated thermistor one end of which contacts the brake fluid 12within the heating vessel. Connected to the heat responsive resistanceelement 26 is a liquid temperature detecting circuit 28, as will laterbe described with reference to FIG. 3. The output terminal of circuit 28is connected an excitation coil 27. The excitation coil 24 controls theopening and closing of a second normally open contact Y2 and secondnormally closed contact X2. As an electric assembly 29 for evaluatingthe quality of the sample brake fluid 12 contained within-theheatingvessel 11 there are provided a first series circuit 291consisting of the first normally closed contact X1, a first lamp L1 andthe second normally open contact Y2, and a second series circuit 292consisting of the first normally open contact Y1, a second lamp L2 andthe second normally closed contact X2. These series circuits 291 and 292are connected in parallel between both the terminals of the DC. powersource 21.

FIG. 2 shows apractical circuit diagram illustrating the conductioncurrent detection circuit 25 of FIG. 1 consisting of a Darlingtoncircuit including a transistor TR1 whose base is connected to the vessel19 and a transistor TR2 whose base is connected to the emitter of thetransistor TRl. The excitation coil 24 is connected between thecollector of the transistor TR2 and the positive terminal 22 of the DC.power source 21. The collector of the transistor TRl is connected via aresistor R1 to the terminal 22 of the DC. power source, and the emitterof the transistor TR2 is connected to ground.

FIG. 3 is a practical circuit diagram showing the liquid temperaturedetection circuit 28 of FIG. 1 which comprises a variable current path32 which is a series circuit consisting of a resistor R11, the aforesaidheat responsive resistance element 26 and a DC. power source 31 whosenegative pole is connected to ground. A series circuit 35 consists of avariable resistor VR and a resistor R12 series connected via a DC.amplifier 34 between ground and a common connection 33 of the resistorR11 to the heat responsive resistance element 26. A Schmidt circuit 37includes a transistor TRll whose base is connected to a common junction36 of the variable resistor VR and the resistor R12. The emitter isconnected to ground via a resistor R13 and the collector is connectedvia a resistor R14 to the positive terminal 22 of the DC. power source21. A transistor TR12 has its emitter connected in common to the emitterof the transistor TRll, and the base is connected via a resistor R15 tothe collector of the transistor TRll and is connected to ground via aresistor R16 and the collector is connected via a resistor R17 to theterminal 22 of the DC. power source 21. A driver circuit 38 includes atransistor TR13 whose base is connected via a resistor R18 to thecollector of the transistor TR12; the emitter is directly connected toground; and the collector is connected via the excitation coil 27 to theterminal 22 of the DC. power source 21.

When the percentage of contained water of an automobile brake fluid ingeneral is more than 3 percent, its boiling point is substantiallydecreased. The results of experiments made by the inventors reveal thatwhen its boiling point is below about C it is necessary to exchange itfor a fresh brake fluid and that a good brake fluid with a water contentof below 3 percent has a boiling point in the temperature range of.about l60-200C. The resistance of the heat responsive resistance element26 is varied as the sample brake fluid 12 within the heating vessel 11is heated by the heater 18. This causes the electric current flowingfrom the DC. power source 31 to the variable current path 32 to bevaried with a corresponding variation in the input voltage of the DC.amplifier 34 appearing across the resistor R11.

Accordingly, the threshold voltage level of the Schmidt circuit 37 ispreset, by adjusting the variable resistor VR in the series circuit 35,at a voltage level representing a boiling point of, for example, about150C at which level it is possible to evaluate the quality of the brakefluid.

According to the liquid quality evaluating apparatus so constructed,when the conduction current detection circuit 25 is rendered conductivebefore the liquid temperature detection circuit 28, the first normallyopen contact Y1 is closed before the second normally open contact Y2. Asa result, the second lamp L2 included in the second series circuit 292of the liquid quality evaluating assembly 29 is lighted before the firstlamp L1 included in the first series circuit 291. The sample brake fluid12 within the heating vessel 11 is thus proved unfit for further use asbrake fluid and replacement is necessary. On the other hand, when theliquid temperature detection circuit 28 is rendered conductive beforethe conduction current detection circuit 25 the second normally opencontact Y2 is closed before the first normally open contact Y1 and thefirst lamp L1 is lighted before the second lamp L2. This indicates thatthe sample brake fluid 12 is still usable.

FIG. 4 is a schematic block diagram showing a further modification ofthe embodiment of FIG. 1. This modification is substantially the same asthe embodiment of FIG. 1 except that the first normally closed contactX1 in the first series circuit 291 and the second normally closedcontact X2 in the second series circuit 292 have been eliminated. Itwill be evident that this modified embodiment can be put to practice inthe same way as the embodiment of FIG. 1 with substantially the sameresult.

FIG. 5 is a schematic block diagram showing another embodiment of aliquid quality evaluating apparatus according to this invention.

This embodiment uses, in place of the liquid temperature detectioncircuit 28, a liquid temperature detection circuit 281 including abridge circuit 42 constituted by the heat responsive resistance element26 and three resistors R21, R22 and R23. A DC. source 41 of about l.5volts is connected across one pair of terminals of the bridge circuit42; and a temperature indicating meter 43 consisting of a conventionalD.C. galvanometer, such as a movable solenoid type is connected betweenthe opposite pair of output terminals of the bridge circuit 42. With theliquid temperature detection circuit 281 so designed, when the resistorsR22 and R23 are preset to be equal in resistance value to each other andthe resistor R21 is preset to be equal in resistance to that of the heatresponsive resistance element 26 under a normal ambient temperature(about -25C), then no output appears, at that temperature. When thebrake fluid 12 within the heating vessel 11 is gradually heated by theheater 18, the resistance of the heat responsive resistance element 26is increased. As a result, a corresponding output voltage appearsbetween the output terminals of the bridge circuit 42. The temperaturerise of the brake fluid causes the resistance of the heat responsiveresistance element 26 to rise causing the pointer 44 of the temperatureindicating meter 43 to be deflected, to represent a temperaturevariation. Also, with the embodiment of FIG. 5, in place of the sampleliquid quality evaluating assemblies utilizing two lamps as in FIGS. 1and 4, an arrangement is used so that when the excitation coil 24 isactuated, a metal piece 46 made of a magnetic conductive material whoseone end is rotatable around a fulcrum is electromagnetically attractedto cause the tip of the pointer 44 of the temperature indicating meter43 to be locked.

According to the liquid quality evaluating apparatus so designed, whenthe pointer 44 is deflected, and locked of a temperature a positionrepresentative at below about 150C on the indicating meter 43 as shownin FIG. 6, the brake fluid 12 should be exchanged. Where the pointer islocked within a boiling temperature range of about l50-I709C'a warningATT is the meter indication. When the pointer 44 is locked at a positionof about 170C, the meter indication is GOOD". As a result, it ispossible to indicate the quality of the brake fluid with a high accuracyand with a simpler structure than the embodiment of FIG. 1.

FIG. 7 show a preferred embodiment of the sealed cover 13 used to closethe heating vessel 11 shown in FIGS. 1, 4 and 5. The seal covering 131of this example has a capillary bore 51 of, for example, about 0.5mm

provided substantially at its center. When the brake fluid 12 within theheating vessel 11 is boiled rapidly through the nozzle 15 into thevessel 19 due to vapor pressure of the boiled brake fluid as well ascapillary action, the bore of the seal covering serves to facilitate thepassage of a gas or air, but prevent the passage of fluid therethrough.It is desirable that the seal covering 131 having the bore 51 be made ofa heat insulating material 52 such as teflon, but it is difficult toprovide in teflon, a bore as small as 0.5mm in diameter and usually lmmis the smallest. As shown in the figure however, on the upper portion ofthe teflon 52 an auxiliary brass covering 53 is provided having a bore512 with a diammeter of about 0.5mm.

FIG. 8 is a schematic block diagram showing a further embodiment of aliquid quality evaluating apparatus.

With this embodiment use is made of a heating vessel 61 made of anelectric and heat conductive material, such as copper, whoselongitudinal cross section is substantially U-shaped. Disposed withinthe vessel 62 is a needle-like electrode 62 one end of which is spacedapart about lmm from the inner bottom surface of the vessel 62. Theother end of the electrode 62 is supported, in an integral fashionthrough an electrical insulating material 63 such as porcelain, on theheating vessel 61 and is connected to the vessel 61 through a resistorR31 and a DC. power source 64 of about 6 volts with the polarityindicated. Across the terminals of the resistor R31 a counter 66 isconnected through a Schmidt circuit 65. Below the heating vessel 61 is aheating source including a heater 67 and a power source 69 connected,through a temperature adjusting element consisting of a variableresistor 68, across the terminals of the heater 67. In the figurereference numeral 71 denotes a coupling capacitor. After the vessel 61is heated to the boiling temperature of an automobile brake fluid havinga water content of about 3 percent for example, C, a sample brake fluid73 of about 0.0l0.03cc is dropped within the heating vessel 61 by aspout 72 in a manner to be in contact with the needle-like electrode 62.This establishes a current conduction path 74 consisting of the heatingvessel 61, the fluid 73, the needle-like electrode 62, the resistor 31and the DC. power source 64. In this case, when the temperature of theheating vessel 61 is below the boiling point of the brake fluid 73; thesample brake fluid is not boiled and a constant voltage Vo of about 6volts substantially equal to a voltage of the DC power source 64 asshown in FIG. 9A is applied to the Schmidt circuit 65. When, on theother hand, the temperature of the heating vessel 61 is higher than theboiling point of the sample corresponding to a water content of morethan 3 percent; then, the sample boils, and bubbles substantiallyproportional to the water content of the brake fluid are produced. Then,a corresponding pulsating signals e1, e2, e3 as shown in FIG. 9A areimpressed on the Schmidt circuit 65 across the terminals of the resistorR31 included in the current conduction path 74. These pulsating signalsare such that their maximum and minimum values are varied within therange of the positive voltage (0 volt) and the negative voltage (6volts) of the DC. power source 64. Therefore, if the threshold voltagelevel S of the Schmidt circuit 65 is preset to a voltage level (theresult of experiments has revealed that about -2 to 3 volts aresuitable) capable of individually detecting each of the pulsatingsignals e1, e2, e3 then pulse signals pl, p2, p3 corresponding to thebubbles produced are driven, as shown in FIG. 98, from the outputterminal of the Schmidt circuit 65. The number of pulse signals iscounted by thecounter 66. When the count reaches a predetermined value,for example, 3, then the brake fluid is evaluated as bad and when thecount is less than 3, the brake fluid is evaluated as good.

It will be understood that the liquid quality evaluating apparatusaccording to this invention can be applied not only to an automobilebrake fluid, but also any other liquid whose'impurity content andboiling point can beforehand be obtained, since they provide a readyevaluation of the quality of the liquid.

While preferred embodiments have been disclosed herein, applicants claimthe benefit of a full range of equivalents within the scope of theappended claims.

What we claim is:

1. Apparatus for determining whether the boiling point of hygroscopicliquid such as automotive brake fluid is at least above or below areference temperature comprising:

a first substantially closed vessel made of heat conductive material forcontaining a predetermined sample of liquid to be tested, said vesselbeing providedwith a nozzle projecting from a side wall, said nozzlehaving at least a portion higher than the level of the sample liquidwithin said vessel; means for controlled heating of said vessel;

a second vessel made of electrically conductive mate rial, positioned toreceive said sample liquid when forced through said nozzle by boiling insaid first vessel;

a needle-like electrode having one end disposed within said secondvessel so as to be in contact with the boiled sample liquid therein;

a current detection circuit forming a closed path through at least theboiled sample liquid within said second vessel and saie needle-likeelectrode for producing an output signal in response to contact of theboiled sample with said electrode;

means for providing a different signal whenever the temperature ofliquid in said first vessel reaches a reference temperature; and

indicating means responsive to said signals to indicate at least whetherthe boiling point of said sample liquid is above or below a referencetemperature.

2. Apparatus as defined by claim 1 in which said vessels aresubstantially U-shaped in cross-section and said first vessel includes acover having a capillary bore extending completely therethrough saidbore having an inside diameter of about 0.5mm.

3. Apparatus as defined by claim 1 in which said means for controlledheating of said first vessel includes an electrically resistive heatingelement connected in series with a variable resistor and a power source.

4. Apparatus as defined in claim I wherein said current detectioncircuit comprises:

an active circuit means having input and output electrodes;

said second vessel;

the boiled sample liquid in said second vessel;

said needle-like electrode;

a DC power source;

an excitation coil;

said input electrode being connected to said source and said outputelectrode being connected through said excitation coil to said source;and wherein said liquid temperature detection circuit comprises:

a variable current path formed by a series circuit including a second DCpower source, a heat responsive resistance element in said first vesseland a resistor;

a DC amplifier having its input connected to said series circuit betweensaid heat responsive resistive element and said resistor;

a Schmidt circuit coupled to the output of said DC amplifier and havinga preset threshold voltage level indicative of a boiling pointsubstantially representing a boundary between good and bad qualities ofthe same type of liquid as the sample liquid on the test;

a driver circuit having its input coupled to the output of said Schmidtcircuit;

a second excitation coil connected between the output of said drivercircuit and said second DC source; I

and wherein said indicating means includes a first normally open lampcircuit arranged to be closed when said second excitation coil isenergized and a second normally open lamp circuit arranged to be closedwhen the other of said excitation coils is energized.

5. Apparatus as defined by claim 1 wherein said current detectioncircuit comprises:

an active circuit element means having input and output electrodes;

said second mentioned vessels;

the boiled liquid in said second vessel;

said needle-like electtode;

a first DC power source;

an excitation coil;

said input electrode being connected to said first DC source and saidoutput electrode being connected through said excitation coil to saidsource;

and wherein said liquid temperature detection circuit comprises:

a bridge circuit one leg of which is a heat responsive resistenceelement in said first vessel;

a second DC source connected across one pair of terminals of said bridgecircuit;

and wherein said indicating means comprises:

a temperature indicating DC galvanometer connected across the oppositepair of terminals of said bridge; and

means responsive to energization of said excitation coil for locking thepointer of said galvanometer.

6. Apparatus for determining whether the boiling point of a hydroscopicliquid such as automotive brake fluid is at least above or below areference temperature comprising:

a heating vessel formed of a material both electrically and heatconductive;

a needle-like electrode having one end disposed in proximity to theinner bottom of said vessel;

a heating source for said vessel including a heater and a power sourcecoupled to said heater;

a current conduction path including said vessel, a

sample liquid poured into said vessel, said needlelike electrode, aresistor connected to the opposite end of said needle-like electrode anda DC power source connected between said vessel and said resistor;

a Schmidt circuit having its input terminals connected across saidresistor and having a preset threshold voltage level; and

a counter coupled to the output of said Schmidt circuit to count anumber of output pulse signals therefrom.

1. Apparatus for determining whether the boiling point of hygroscopicliquid such as automotive brake fluid is at least above or below areference temperature comprising: a first substantially closed vesselmade of heat conductive material for containing a predetermined sampleof liquid to be tested, said vessel being provided with a nozzleprojecting from a side wall, said nozzle having at least a portionhigher than the level of the sample liquid within said vessel; means forcontrolled heating of said vessel; a second vessel made of electricallyconductive material, positioned to receive said sample liquid whenforced through said nozzle by boiling in said first vessel; aneedle-like electrode having one end disposed within said second vesselso as to be in contact with the boiled sample liquid therein; a currentdetection circuit forming a closed path through at least the boiledsample liquid within said second vessel and saie needle-like electrodefor producing an output signal in response to contact of the boiledsample with said electrode; means for providing a different signalwhenever the temperature of liquid in said first vessel reaches areference temperature; and indicating means responsive to said signalsto indicate at least whether the boiling point of said sample liquid isabove or below a reference temperature.
 2. Apparatus as defined by claim1 in which said vessels are substantially U-shaped in cross-section andsaid first vessel includes a cover having a capillary bore extendingcompletely therethrough said bore having an inside diameter of about0.5mm.
 3. Apparatus as defined by claim 1 in which said means forcontrolled heating of said first vessel includes an electricallyresistive heating element connected in series with a variable resistorand a power source.
 4. Apparatus as defined in claim 1 wherein saidcurrent detection circuit comprises: an active circuit means havinginput and output electrodes; said second vessel; the boiled sampleliquid in said second vessel; said needle-like electrode; a DC powersource; an excitation coil; said input electrode being connected to saidsource and said output electrode being connected through said excitationcoil to said source; and wherein said liquid temperature detectioncircuit comprises: a variable current path formed by a series circuitincluding a second DC power source, a heat responsive resistance elementin said first vessel and a resistor; a DC amplifier having its inputconnected to said series circuit between said heat responsive resistiveelement and said resistor; a Schmidt circuit coupled to the output ofsaid DC amplifier and having a preset threshold voltage level indicativeof a boiling point substantially representing a boundary between goodand bad qualities of the same type of liquid as the sample liquid on thetest; a driver circuit having its input coupled to the output of saidSchmidt circuit; a second excitation coil connected between the outputof said driver circuit and said second DC source; and wherein saidindicating means includes a first normally open lamp circuit arranged tobe closed when said second excitation coil is energized and a secondnormally open lamp circuit arranged to be closed when the other of saidexcitation coils is energized.
 5. Apparatus as defined by claim 1wherein said current detection circuit comprises: an active circuitelement means having input and output electrodes; said second mentionedvessels; the boiled liquid in said second vessel; said needle-likeelecttode; a first DC power source; an excitation coil; said inputelectrode being connected to said first DC source and said outputelectrode being connected through said excitation coil to said source;and wherein said liquid temperature detection circuit comprises: abridge circuit one leg of which is a heat responsive resistence elementin said first vessel; a second DC source connected across one pair ofterminals of said bridge circuit; and wherein said indicating meanscomprises: a temperature indicating DC galvanometer connected across theopposite pair of terminals of said bridge; and means responsive toenergization of said excitation coil for locking the pointer of saidgalvanometer.
 6. Apparatus for determining whether the boiling point ofa hydroscopic liquid such as automotive brake fluid is at least above orbelow a reference temperature comprising: a heating vessel formed of amaterial both electrically and heat conductive; a needle-like electrodehaving one end disposed in proximity to the inner bottom of said vessel;a heating source for said vessel including a heater and a power sourcecoupled to said heater; a current conduction path including said vessel,a sample liquid poured into said vessel, said needle-like electrode, aresistor connected to the opposite end of said needle-like electrode anda DC power source connected between said vessel and said resistor; aSchmidt circuit having its input terminals connected across saidresistor and having a preset threshold voltage level; and a countercoupled to the output of said Schmidt circuit to count a number ofoutput pulse signals therefrom.